Feed control device

ABSTRACT

A clutch normally connects a driving wheel to a rotating drive shaft which controls the linear advance of a tool into a workpiece. The clutch is set to slip when the torque transmitted therethrough exceeds a predetermined limit, thereby ceasing advance of the tool while permitting the driving wheel to continue its rotation. The maximum advance of the tool is controlled by a stop arm which rotates with the drive shaft and which can be angularly adjusted thereon. Advance of the tool continues until the stop arm engages a micrometer-type adjustable stop, at which point the torque applied to the clutch exceeds its predetermined capacity, causing the clutch to slip and advance of the tool to cease.

United States Patent Edward M. Newsome 25700 DHondt Court, Chesterfield Township, Mich. 48043 Inventor Primary ExaniinerAllan D. Herrmann Attorney-Cullen, Settle, Sloman 8r. Cantor ABSTRACT: A clutch nonnally connects a driving wheel to a rotating drive shaft which controls the linear advance of a tool into a workpiece. The clutch is set to slip when the torque transmitted therethrough exceeds a predetermined limit, thereby ceasing advance of the tool while permitting the driving wheel to continue its rotation. The maximum advance of the tool is controlled by a stop arm which rotates with the drive shaft and which can be angularly adjusted thereon. Advance of the tool continues until the stop arm engages a micrometer-type adjustable stop, at which point the torque applied to the clutch exceeds its predetermined capacity, causing the clutch to slip and advance of the tool to cease.

PATENTEDOCHZIHTI 3,612,238

INVENTOR.

EDWARD M. AEWSOME CULLBV,SETTLE, SLOMAN 6 cmwm.

ATT'YS.

FEED CONTROL nsvrcs BRIEF DESCRIPTION OF THE DRAWINGS DETAILEDDESCRIPT ION OF THE DISCLOS'URE Referring to FIG. 2 in particular of the drawings, the invention generally comprises a machine'base or housing upon which a traversing table 12 is mounted for reciprocating linear movement. Base 10 and traversing table 12 are only fragmentarily illustrated, their details being .not essential to the un-' derstanding of this invention. The machine might be a grinding or cutting machine with the grinding wheel or cutting tool being carried upon traversing table 12 for advancement into the workpiece. The mechanism to be described below is particularly intended for use in grinding operations on a large number of identical pieces, and reduces the number of measurements required by providing a preprogrammed indication of when the desired dimension has been reached.

Traversing table I2 is caused to move by drive shaft I4 having a threaded lead screw portion 16 which engages a nut portion I8 of table I2. A driving wheel 20 is rotatably mounted upon clutch assembly 22 which is in turn keyed or splined to drive shaft 14 at 24. Driving wheel 20, which may be a ratchet wheel or a conventionally toothed gear, is caused to rotate by its engagement with a powered driving element 25, which in turn may be a pawl, rack or another gear.

Clutch assembly 22 comprises left and right clutch elements 26 and 28, each of which is splined at 24 to shaft 14 for rotation therewith. This splined connection permits axial movement of the clutch elements along shaft 14. Each of clutch elements 26 and 28 is provided with an annular clutch plate 30 fabricated of a suitable clutch-facing material having a low coefficient of friction. Clutch elements 26 and 28 are biased toward each other by a series of angularly spaced springs 32 compressed between a socket in left clutch element 26 and a bolt and washer assembly 34 which is threaded into right clutch element 28. Clutch assembly 22 is calibrated to provide a driving connection between driving wheel 20 and drive shaft I4 until a predetermined maximum torque is reached, at which point the clutch begins to slip.

Referring now to FIG. I (from which some of the com-.

ponents have been omitted for clarity) and 2 of the drawings, the stop portion of this invention generally comprises a stop arm 36 and clamping wheel 38 carried by drive shaft 14, and a micrometer stop assembly 40 mounted to the base or housing 10 of the machine. A hand wheel 41 is keyed to shaft 14 so, that the shaft can be manually turned if desired. Wheel 4], however, is free to slide axially along the shaft. Stop arm 36 is rotatably mounted on a tapered portion 42 of shaft 14. It can be clamped to the shah for rotation therewith when clamping wheel 38, which is threaded onto a'threaded portion 44 of drive shaft 14, is advanced toward the right in FIG. 2. Such movement of wheel 38 causes it to slide washer .46 to the right, which in turn forces hand wheel 41 against stop arm 36, thus securely clamping stop arm 36 against the tapered section 42 of the drive shaft.

Micrometer stop assembly 40 comprises a stop 48 which is axially extendable relative to stop assembly 40 by a conventional-type of calibrated micrometer adjustment knob 50.

An enlargement of adjustable stop 48 is illustrated in FIG. 3, along with a schematic representation of an optional accessory control circuit. Embedded within the top of stop 48 is sensor 52 of a conventional radio-frequency-type proximity switch. Sensor 52 is electrically insulated from stop 48 by insulation block 54. Sensor 52 is connected to a conventional RF generating circuit by lead wire 36. In such proximity switches, sensor 52 acts as an antenna to radiate an RF signal until stop 36 abuts its tip, at which time the radiation is shut off and current ceases to flow in lead wire 56.

Lead wire 56 can form the actuating coil of a relay 58, which in turn can open or close a circuit controlling some portion of the machine. For example, relay 58 can shut off a motor driving the grinding wheel or reciprocating the workpiece past the grinder. As another application of the proximity switch, the relay could control a timer or counter which regulates how long the workpiece continues to be reciprocated the grinder after grinder advance has ceased, thereby controlling polishing time.

OPERATION As referred. to above, the mechanism described above is particularly well suited for use in grinding a large number of identical workpieces, such as cutting tools, to a precise finished dimension.

In use, the first of a series of identical workpieces would be ground to almost its final size in the conventional manner. During this operation, clamping wheel 38 is loosened so that stop arm 36 hangs freely on shaft 14. The workpiece is then measured with a micrometer, and the amount ofmaterial yet to be removed is determined. That distance of further advance required of table I2 is then converted to degrees of rotation of lead screw 16 and then to distance along the are on which the stop-contacting point of stop arm 36 swings, using the known dimensions of the machine.

For example, assume that the lead screw has l2 threads per inch, so that one revolution produces 0.0833 inch of advance of table I2, which equals 0.00023 inch of advance per degree of rotation. "the radius from the axis of lead screw shaft I4 out to the point of contact between stop arm 36 and stop 48 were six inches, then 0.00023 inch of advance or one degree of shaft rotation would correspond to about 0.l05 inch of travel of stop arm 36 at such contact point. This amounts to a magnification of 456 times in terms of travel of stop 48.

So, assume that a preliminary measurement of the work piece indicated that 0.0015 inch of material had, to be removed. Next, the operator would swing stop arm 36 into contact with stop 48, which could be set at any convenient point to simplify the arithmetic, and clamp it securely with wheel 38. The operator would then convert the 0.00] 5 inch of additional feed required to 0.684 inch of stop movement, using the 456 magnification factor. Using calibrated knot 50, stop 48 is then shifted 0.684 inch to permitthe necessary additional travel of stop arm 36, lead screw I6, and table 12.

Grinding is then resumed until stop arm 36 engages stop 48, at which point the torque being transmitted through clutch 22 will immediately exceed its capacity, causing it to slip. Thus, lead screw ceases to turn, through driving wheel 20 may continue to rotate, arid further advance of table I2 ceases at the desired finished dimension of the workpiece.

Thereafter, allsubsequent identical workpieces can be final ground without the need for any measurements, since grinder advance will automatically cease at the proper point because of the preset setting of positive stop 48.

Reliability and uniformity of results is extremely high not only because of a precisely positioned positive stop, but also because a pressure (that is, the torque limit of the calibrated clutch) actually determines the stop point. Advance continues until the clutch slips.

Thus, if driving element 25 is responsive to a reciprocating feed of the workpiece past the now stationary grinder, such feed can continue, without further advance of the grinder, producing a polishing action. In this regard, the structure shown in FIG. 3 offers still further advantages. As described above, relay 58 can be employed ,to effect an immediate shut- 7 down of all movement, or it can be used to provide a uniform time of number of cycles of continued polishing following engagement of stop arm 36 with stop 48. This provides still further control of uniformity and precision of results.

This invention may be further developed within the scope of the following claims. Accordingly, the above specification is to be interpreted as illustrative of only a single operative embodiment of this invention, rather than in a strictly limited sense.

I now claim:

1. In a machine wherein a cutting or grinding tool or the like operates upon a workpiece and advances relative thereto when a rotatable drive shaft to which the tool is connected is selectively connected to a powered driving element, the improved means for accurately controlling the ultimate position of the advancing tool which comprises:

a driving wheel rotatably mounted on the drive shaft, said driving wheel being continuously rotated by an engagement with the powered driving element;

clutch means fixed to the drive shaft for rotation therewith,

said clutch means normally being in frictional engagement with said driving wheel to cause the drive shaft to be normally connected to said driving wheel for rotation thereby, but said clutch means disengaging said driving wheel from said drive shaft when the torque on said clutch means exceeds the predetennined limit;

a stop arm rotatably mounted on the drive shaft;

clamping means mounted on the drive shaft for selectively securely clamping said stop arm to the drive shafi for rotation therewith;

and a calibrated stop adjustably mounted on the machine in the path of said stop arm to cause said stop arm and the drive shaft to cease rotation when said stop arm, in its clamped condition, comes into contact with said stop, the stopping of the drive shaft causing said clutch to slip to permit said driving wheel to continue rotation.

2. The improved control device of claim 1 which further comprises a proximity switch mounted on one of the abuttable surfaces of said stop arm or said calibrated stop, said proximity switch connected to an electrical circuit controlling a selected portion of the machine.

3. The improved control device of claim 2 wherein said proximity switch is an RF-type switch.

l0l005 D453 

1. In a machine wherein a cutting or grinding tool or the like operates upon a workpiece and advances relative thereto when a rotatable drive shaft to which the tool is connected is selectively connected to a powered driving element, the improved means for accurately controlling the ultimate position of the advancing tool which comprises: a driving wheel rotatably mounted on the drive shaft, said driving wheel being continuously rotated by an engagement with the powered driving element; clutch means fixed to the drive shaft for rotation therewith, said clutch means normally being in frictional engagement with said driving wheel to cause the drive shaft to be normally connected to said driving wheel for rotation thereby, but said clutch means disengaging said driving wheel from said drive shaft when the torque on said clutch means exceeds the predetermined limit; a stop arm rotatably mounted on the drive shaft; clamping means mounted on the drive shaft for selectively securely clamping said stop arm to the drive shaft for rotation therewith; and a calibrated stop adjustably mounted on the machine in the path of said stop arm to cause said stop arm and the drive shaft to cease rotation when said stop arm, in its clamped condition, comes into contact with said stop, the stopping of the drive shaft causing said clutch to slip to permit said driving wheel to continue rotation.
 2. The improved control device of claim 1 which further comprises a proximity switch mounted on one of the abuttable surfaces of said stop arm or said calibrated stop, said proximity switch connected to an electrical circuit controlling a selected portion of the machine.
 3. The improved control device of claim 2 wherein said proximity switch is an RF-type switch. 